U.S. patent application number 10/192665 was filed with the patent office on 2002-12-19 for conductive cap, electronic component, and method of forming insulating film of conductive cap.
This patent application is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Baba, Toshiyuki, Inoue, Jiro, Kawabata, Shoichi, Kitagawa, Tsuyoshi, Nishimura, Toshio.
Application Number | 20020189832 10/192665 |
Document ID | / |
Family ID | 27331834 |
Filed Date | 2002-12-19 |
United States Patent
Application |
20020189832 |
Kind Code |
A1 |
Baba, Toshiyuki ; et
al. |
December 19, 2002 |
Conductive cap, electronic component, and method of forming
insulating film of conductive cap
Abstract
A conductive cap for use in an electronic component, has an
opening at a bottom portion thereof, and is constructed to be fixed
to the upper surface of a substrate of the electronic component at
the opening portion of the cap so as to cover at least an
electronic component element mounted on the upper surface of the
substrate having terminal electrodes provided thereon. The end
surface of the opening and the inner and outer surfaces thereof in
connection to and in the vicinity of the end surface are provided
with an insulating film disposed thereon.
Inventors: |
Baba, Toshiyuki;
(Moriyama-shi, JP) ; Nishimura, Toshio;
(Shiga-ken, JP) ; Kitagawa, Tsuyoshi; (Toyama-ken,
JP) ; Inoue, Jiro; (Omihachiman-shi, JP) ;
Kawabata, Shoichi; (Otsu-shi, JP) |
Correspondence
Address: |
KEATING & BENNETT LLP
Suite 312
10400 Eaton Place
Fairfax
VA
22030
US
|
Assignee: |
Murata Manufacturing Co.,
Ltd.
Nagaokakyo-shi
JP
|
Family ID: |
27331834 |
Appl. No.: |
10/192665 |
Filed: |
July 11, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10192665 |
Jul 11, 2002 |
|
|
|
09642486 |
Aug 18, 2000 |
|
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Current U.S.
Class: |
174/358 ;
174/370; 257/E23.191; 257/E23.193 |
Current CPC
Class: |
H01L 2924/01078
20130101; H01L 21/4803 20130101; H01L 2924/16152 20130101; H01L
2924/3011 20130101; H01L 2224/16 20130101; H01L 2924/3025 20130101;
H01L 23/06 20130101; H01L 23/10 20130101; H01L 2924/01068 20130101;
H01L 2924/09701 20130101 |
Class at
Publication: |
174/35.00R |
International
Class: |
H05K 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 18, 1999 |
JP |
11-231988 |
Aug 18, 2000 |
JP |
11-231989 |
Oct 7, 1999 |
JP |
11-287217 |
Claims
What is claimed is:
1. A conductive cap for use in an electronic component, the
conductive cap comprising: an upper surface, a lower surface and
inner and outer side surfaces; an opening on the lower surface
thereof, the cap being adapted to be fixed to the upper surface of
the substrate of the electronic component on the opening side of
the cap so as to cover at least an electronic component element
mounted on the upper surface of the substrate having terminal
electrodes disposed thereon; wherein an end surface of said opening
and the inner and outer side surfaces thereof in connection to and
in the vicinity of the end surface are provided with an insulating
film formed thereon.
2. A conductive cap according to claim 1, wherein the insulation
resistance between the opening end surface of the conductive cap
and the outer side of the insulation film is at about least
10.sup.9 .OMEGA..
3. A conductive cap according to claim 1, wherein the thickness of
said insulating film is in the range of about 4 .mu.m to about 25
.mu.m.
4. A conductive cap according to claim 1, wherein when the opening
end surface of the conductive cap and an adjacent portion thereof
are viewed in a section taken substantially perpendicularly
relative to the circumferential direction of the conductive cap,
the opening end surface of the cap and the inner side surface
thereof in connection to the opening end surface define a curved
line, and the radius R of curvature of the curved line is in the
range of about 80 .mu.m to about 150 .mu.m.
5. An electronic component comprising: a substrate having a
plurality of terminal electrodes disposed on at least an upper
surface thereof; an electronic component element fixed to the
substrate and electrically connected to the plurality of terminal
electrodes; and a conductive cap having an opening on a lower
surface thereof and an insulating film provided on the opening end
surface thereof and an adjacent portion, and bonded to the
substrate on the opening side thereof.
6. An electronic component according to claim 5, wherein said
electronic component element is a piezoelectric element.
7. An electronic component according to claim 5, wherein the
conductive cap is a metallic cap.
8. A method of forming an insulating film of a conductive cap, the
method comprising the steps of: holding a plurality of conductive
caps each having an opening on a lower surface thereof while the
conductive caps are arranged by a holding device; pressing the
opening end surface side of the plurality of conductive caps held
by the holding device against a resin layer for forming an
insulating film having a predetermined thickness, and thereafter
separating the conductive caps from the resin layer for forming an
insulating film, whereby the insulating film is formed on the
opening end surface of each conductive cap and the vicinity of the
opening end surface by a transfer method; and drying the insulating
film after the transfer step.
9. A method of forming an insulating film of a conductive cap
according to claim 8, wherein the resin used for forming an
insulating film is a resin having a viscosity at about
25.+-.5.degree. C. of about 5000 cps to about 20000 cps.
10. A method of forming an insulating film of a conductive cap for
sealing an electronic component, the method comprising the steps
of: providing a conductive cap being adapted to be fixed to the
surface of a substrate having terminal electrodes formed thereon so
as to cover and seal an element mounted to the surface of the
substrate; forming an insulating film on the conductive cap so that
the insulating film electrically insulates the terminal electrodes
from the conductive cap; wherein the conductive cap is made of one
of aluminum and an aluminum alloy, and the insulating film is
formed on the surface of the conductive cap by anodization carried
out in the cap-shaped state.
11. A method of forming an insulating film of a conductive cap
according to claim 10, wherein the anodization is carried out while
the conductive cap is held by a jig and is electrically
connected.
12. A method of forming an insulating film of a conductive cap
according to claim 10, wherein after a sheet material is punched to
form caps, the anodization is carried out while the caps are
partially connected to the sheet material and kept in a hoop
state.
13. A method of forming an insulating film of a conductive cap
according to claim 12, wherein the hoop is fed into the anodization
bath, and after the anodization, the hoop is wound, whereby the
anodization is continuously carried out.
14. A method of forming an insulating film of a conductive cap
according to claim 12, wherein the hoop is cut to a predetermined
unit length and is dipped into an anodization bath to be
anodization-treated.
15. A conductive cap for sealing an electronic component, the
conductive cap comprising: a cap body including a lower surface
which is adapted to be fixed to a surface of a substrate of the
electronic component so as to cover and seal an element mounted
onto the surface of the substrate having terminal electrodes
disposed thereon, the conductive cap body is made of one of
aluminum and an aluminum alloy; and an insulating film is disposed
at least on the surface portions of the conductive cap to be
contacted with the terminal electrodes.
16. A method of forming an insulating film of a conductive cap for
sealing an electronic component, the method comprising the steps
of: providing a conductive cap adapted to be fixed to the surface
of the substrate of the electronic component having terminal
electrodes disposed thereon so as to cover and seal an element
mounted onto the surface of the substrate; forming an insulating
film on the conductive cap so that the insulating film electrically
insulates the terminal electrodes from the conductive cap; wherein
the insulating film is formed on the surface of the conductive cap
by electrodeposition coating.
17. A method of forming an insulating film of a conductive cap
according to claim 16, further comprising the steps of bonding a
conductive double side adhesion tape to a conductive supporting
sheet, and bonding the conductive cap to the conductive double side
adhesion tape, so that the conductive cap is electrically
connected, supported, and electrodeposition-coated.
18. A method of forming an insulating film of a conductive cap
according to claim 16, wherein the electrodeposition coating is
carried out while the conductive cap is supported by a jig and
electrically connected.
19. A conductive cap for sealing an electronic component,
comprising: a conductive cap body that is adapted to be fixed to a
surface of a substrate of the electronic component having terminal
electrodes disposed thereon so as to cover and seal an element
mounted onto the surface of the substrate; and an insulating film
disposed at least on the portions of the conductive cap to be
contacted with the terminal electrodes.
20. A conductive cap for covering and sealing an element mounted
onto the surface of a substrate having terminal electrodes formed
thereon, wherein said conductive cap has an insulating film
disposed at least on the surface of the portions of the cap that
are arranged to contact the terminal electrodes.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a conductive cap for
covering an electronic element such as a piezoelectric element
mounted on the upper surface of a substrate, an electronic
component including such a conductive cap, and a method of forming
an insulating film of the conductive cap.
[0003] 2. Description of the Related Art
[0004] For conventional electronic component elements such as
piezoelectric resonators or other suitable components, a package
structure including a conductive cap has been used. Such a type of
package structure will be described with reference to FIG. 6.
[0005] The package structure contains a substrate 51 having a
rectangular sheet shape, made of an insulating material such as
alumina, and a metallic cap 52. On the upper surface 51a of the
substrate 51, terminal electrodes 53 and 54 for achieving external
electric connection are provided. The terminal electrodes 53 and 54
each are extended onto the side surfaces, the end surfaces, and the
lower surface, in addition to the upper surface 51a, so that the
package structure can be surface-mounted onto a printed circuit
board.
[0006] Further, a piezoelectric element is mounted onto the upper
surface 51a of the substrate 51 by solder, a conductive bonding
agent such as a conductive adhesive, or the like, though not shown
in FIG. 6. The electrodes of the piezoelectric element are
connected to the terminal electrodes 53 and 54, respectively.
[0007] For the purpose of sealing the piezoelectric element, a
metallic cap 52 having an opening at the lower portion thereof is
bonded to the substrate 51. A rectangular frame-shaped insulating
film 55 is provided on the portion of the upper surface 51a of the
substrate 51 that is arranged to be contacted with the end surface
of the opening of the metallic cap 52. The insulating film 55 is
formed by printing synthetic resin, or printing and baking glass.
The thickness of the insulating film 55 is about 0.1 mm.
Accordingly, the height of the chip electronic component to be
produced can be reduced, even though the metallic cap 52 is
used.
[0008] In recent years, it has been required to reduce the mounting
areas of electronic components. With even greater miniaturization
of components, it has been very difficult to print and form the
insulating film 55 on the upper surface 51a of the substrate 51
with high precision.
[0009] Further, Japanese Unexamined Patent Application Publication
No. 6-132762 discloses an electronic component 71 having a cap
shown in FIG. 7. In this electronic component 71, terminal
electrodes 73 and 74 each extends on the upper surface, the side
surfaces, and lower surface of a substrate 72 made of an insulating
material. A piezoelectric element 75 is bonded to the terminal
electrodes 73 and 74 via solder members 76 and 77.
[0010] A metallic cap 78 is bonded to the upper surface of the
substrate 72 by an insulating adhesive. In order to prevent the
terminal electrodes 73 and 74 and the metallic cap 78 from
short-circuiting, an insulating film 79 is disposed on the entire
inner surface of the metallic cap 78.
[0011] In the prior art, no method of forming the insulating film
79 is specifically described. It is presumed that the insulating
layer is precoated on a sheet material before the material is
shaped into the metallic cap 78, and the precoated sheet material
is formed to have the same shape as that of the cap.
[0012] When the metallic cap described in Japanese Unexamined
Patent Application Publication No. 6-132762 is produced, the
peripheral portion of the opening of the metallic cap 78 must be
bent outward, as shown in FIG. 7, so that the insulating layer is
always positioned on the portions of the terminal electrodes 73 and
74 to be contacted with the metallic cap 78. Accordingly, the
process of producing the metallic cap 78 becomes complicated.
Further, in some cases, when such bending work is carried out, the
insulating layer 79 is peeled, making it impossible to reliably
provide electrical insulation between the metallic cap 78 and the
terminal electrodes 73 and 74.
[0013] In a chip electronic component in which an element such as a
piezoelectric element or other electronic element is mounted onto a
substrate, the piezoelectric vibration portion thereof is vibrated.
As a result, the structure is such that the element is accommodated
in a package that does not interfere with vibration of the element.
After the element is mounted onto the surface of the substrate, a
cap is fixed to the surface of the substrate to cover and seal the
element.
[0014] FIG. 20 is a cross-sectional view showing an example of
another conventional electronic component sealed with such a cap.
In the conventional electronic component shown in FIG. 20, an
insulating cap 30 is used. This is because the cap 30 is fixed to
terminal electrodes 11 and 12 provided on a substrate 10 and must
be insulative in order to prevent the terminal electrodes 11 and 12
from short-circuiting. An element such as a piezoelectric resonator
is mounted onto the upper surface of the substrate 10. The element
20 is bonded to the terminal electrode 11 via solder 21 and the
terminal electrode 12 with solder 22. A terminal electrode 13 is
provided between the terminal electrodes 11 and 12 between the
terminal electrodes 11 and 12 on the lower surface of the substrate
10 to produce a capacitor between the terminal electrodes 11, 12
and 13.
[0015] As the insulating cap 30, a ceramic cap, a resin cap, or
other cap is used. However, these caps must have a thickness of
0.25 mm or larger because of the forming capabilities and
limitations. Accordingly, it is not possible to reduce the height
of the electronic component, and the area of the substrate becomes
larger.
[0016] For the purpose of reducing the height of the electronic
component and enhancing the integration density of the circuit
board, it is preferable to use a metallic cap. However, if the
metallic cap alone is fixed to the substrate, the terminal
electrodes short-circuit, as described above.
[0017] In order to prevent the terminal electrodes from
short-circuiting as described above, a method in which an
insulating layer 31 is disposed on the substrate 10 and the
terminal electrodes 11 and 12 onto which the metallic cap 32 is to
be mounted, and the cap 31 is mounted onto the insulating layer 31,
as shown in FIG. 21. In FIG. 21, elements such as a piezoelectric
resonation element mounted onto the substrate 10 are omitted.
[0018] According to a method as described above, the metallic cap
can be used. Thus, the height of an electronic component can be
reduced. On the other hand, there arises the problem that with
further miniaturization of the electronic component, it becomes
more difficult to form the insulating layer on the substrate with
high precision.
[0019] Japanese Unexamined Utility Model Application Publication
No. 62-158828 and Japanese Unexamined Patent Application
Publication No. 8-204491 disclose an electronic component provided
with a metallic cap that is made of an aluminum sheet having an
anodized film on the surface thereof. However, for the metallic
cap, a sheet material is anodized. Therefore, in the case where the
sheet material is formed into a cap shape, the end surfaces of the
cap to be contacted with terminal electrodes on a substrate have no
anodized films thereon. Accordingly, the terminal electrodes can
not be prevented from short-circuiting.
[0020] Moreover, Japanese Unexamined Patent Application Publication
No. 6-132762 discloses a metallic cap provided with an insulating
layer disposed on the inner surface thereof. Such a metallic cap is
shaped so that the end portions of the cap to be contacted with a
substrate are bent outward, and the inner surface of the cap can be
contacted with terminal electrodes. Accordingly, the insulating
layer disposed on the inner surface is contacted with the terminal
electrodes. Thus, the insulating layer is interposed between the
metallic cap and the terminal electrodes, whereby the terminal
electrodes can be prevented from short-circuiting.
[0021] In Japanese Unexamined Patent Application Publication No.
6-132762, a method of forming the insulating layer is not
specifically described. It is presumed that the insulating layer is
precoated on a sheet material before the material is formed in the
metallic cap shape, and the precoated sheet material is formed into
the cap shape. In the case of such a metallic cap, the end portions
of the cap are bent outward so that the insulating layer on the end
portions of the cap is positioned on the portions of the cap to be
contacted with the terminal electrodes. Further, during bending,
the insulating layer may be peeled so that the insulating
properties become insufficient.
[0022] In some cases, it is necessary to provide an insulating
layer for the outer surface of the metallic cap, so that insulation
between the electronic component and other elements is maintained
when the electronic component is mounted onto a circuit board. In
Japanese Unexamined Patent Application Publication No. 6-132762,
only a method of forming the insulating layer on the inner surface
of the cap is disclosed.
SUMMARY OF THE INVENTION
[0023] In order to overcome the problems described above, preferred
embodiments of the present invention provide a conductive cap that
is adapted to be insulated from terminal electrodes on a substrate
electrically and securely, is produced in a simple process, and
reduces the size and height of an electronic component attributed
to the conductive cap included in the component. Preferred
embodiments of the present invention also provide an electronic
component containing the conductive cap, and a method of forming an
insulating film of the conductive cap.
[0024] According to a preferred embodiment of the present
invention, a conductive cap for use in an electronic component
including an opening at the lower portion thereof, and being
adapted to be fixed to the upper surface of the substrate of the
electronic component on the opening side of the cap so as to cover
at least an electronic component element mounted on the upper
surface of the substrate having terminal electrodes provided
thereon, wherein the end surface of the opening and the inner and
outer side surfaces thereof in connection to and in the vicinity of
the end surface are provided with an insulating film disposed
thereon.
[0025] The insulation resistance between the opening end surface of
the conductive cap and the outer side of the insulation film may be
at least about 10.sup.9 .OMEGA..
[0026] The thickness of said insulating film may be in the range of
about 4 .mu.m to about 25 .mu.m.
[0027] Preferably, when the opening end surface of the conductive
cap and its adjacent portion thereof are viewed in a section taken
perpendicularly relative to the circumferential direction of the
conductive cap, the opening end surface of the cap and the inner
side surface thereof in connection to the opening end surface
define a curved line, and the radius R of curvature of the curved
line is in the range of about 80 .mu.m to about 150 .mu.m.
[0028] According to another preferred embodiment of the present
invention, an electronic component includes a substrate having a
plurality of terminal electrodes provided at least on the upper
surface thereof, an electronic component element fixed to the
substrate and electrically connected to the plurality of terminal
electrodes, and a conductive cap having an opening at the lower
portion thereof, provided with an insulating film disposed on the
opening end surface thereof and its vicinity and bonded to the
substrate on the opening side thereof.
[0029] In the electronic component, the electronic component
element may be a piezoelectric element or other suitable electronic
component.
[0030] Further, in the electronic component, the conductive cap may
be a metallic cap.
[0031] According to a preferred embodiment of the present
invention, a method of forming an insulating film of a conductive
cap includes the steps of holding a plurality of conductive caps
each having an opening at the lower portion thereof while the
conductive caps are arranged by a holding device, pressing the
opening end surface of the plurality of conductive caps held by the
holding device against a resin layer for forming an insulating film
having a predetermined thickness, separating the conductive caps
from the resin layer for forming an insulating film, whereby the
insulating film is formed on the opening end surface of each
conductive cap and its vicinity of the opening end surface by the
transfer method, and drying the insulating film after the transfer
step.
[0032] In the method, as the resin for forming an insulating film,
a resin having a viscosity at about 25.+-.5.degree. C. of about
5000 to about 20000 cps may preferably be used.
[0033] According to another preferred embodiment of the present
invention, a method of forming an insulating film of a conductive
cap for sealing an electronic component includes the steps of
providing a conductive cap that is adapted to be fixed to the
surface of a substrate having terminal electrodes disposed thereon
so as to cover and seal an element mounted to the surface of the
substrate, the insulating film being adapted to electrically
insulate the terminal electrodes from the metallic cap, wherein the
conductive cap is made of aluminum or an alloy thereof, and forming
an insulating film on the surface of the conductive cap by
anodization carried out in the cap-shaped state.
[0034] As described above, the anodization is carried out in the
cap-shaped state. Accordingly, the insulating film can be formed by
the anodization on the surface portions of the conductive cap to be
contacted with the terminal electrodes when the conductive cap is
fixed to the surface of the substrate. Hence, such a metallic cap
alone can be fixed to the surface of the substrate by an adhesive
or other joining material or element to achieve sealing.
[0035] The anodization can be performed under the general
anodization conditions. An oxidized film can be electrolytically
formed on the metallic cap so as to define an anode. As an
electrolyte, generally-used acidic electrolytes such as sulfuric
acid, oxalic acid, chromic acid, and so forth may be preferably
used.
[0036] Preferably, the anodization is carried out while the
conductive cap is held by a jig and is electrically connected. As
the jig, a conductive jig is preferably used, and is electrically
connected to the metallic cap. The conductive cap as an anode is
electrolytically treated. This method is suitable in the case where
the conductive caps are individually separated and are separate
from each other.
[0037] Preferably, the anodization is carried out while the
conductive caps are connected to each other in a hoop-shape state.
In the hoop-shape state, a sheet material and the caps are
partially connected to each other after the sheet material is
punched and shaped into caps.
[0038] In such a hoop-shape state, the anodization can be
continuously carried out. That is, for the continuous anodization,
the hoop wound around one roll or the like is unwound and fed into
an anodization bath, and after the anodization, is taken up around
the other roll. In this case, the electrical conduction state of
the hoop can be kept by moving a contact for electrically
connecting the hoop correspondingly to the movement of the
hoop.
[0039] Further, the hoop cut to a predetermined unit length may be
dipped into an anodization bath to be anodization-treated. In this
case, by utilizing a piece for holding each cut hoop as a contact,
the cut hoop can be electrically connected.
[0040] Further, according to another preferred embodiment of the
present invention, there is provided a conductive cap for sealing
an electronic component, the cap being adapted to be fixed to the
surface of the substrate of the electronic component so as to cover
and seal an element mounted onto the surface of the substrate
having terminal electrodes disposed thereon, wherein the conductive
cap is made of aluminum or an alloy thereof, and an insulating film
is formed by anodization at least on the surface portions of the
conductive cap to be contacted with the terminal electrodes.
[0041] The conductive cap of various preferred embodiments of the
present invention can be produced according to the method of
forming an insulating film of another preferred embodiment of the
present invention. The conductive cap of various preferred
embodiments of the present invention alone can be fixed to the
surface of the substrate by an adhesive or other joining material
or element, since the insulating film is formed at least on the
surface portions of the conductive cap to be contacted with the
terminal electrodes, thereby securing the insulation between the
terminal electrodes on the substrate and the conductive cap. Thus,
an electronic component having a greatly reduced height is
efficiently produced.
[0042] According to another preferred embodiment of the present
invention, a method of forming an insulating film of a conductive
cap for sealing an electronic component, which is fixed to the
surface of the substrate of the electronic component having
terminal electrodes disposed thereon so as to cover and seal an
element mounted onto the surface of the substrate, the insulating
film being adapted to electrically insulate the terminal electrodes
from the conductive cap, wherein the insulating film is formed on
the surface of the conductive cap by electrodeposition coating.
[0043] According to this preferred embodiment of the present
invention, the insulating film can be formed in the cap-shaped
state. Accordingly, for any cap-shape, the insulating film can be
formed on the surface of the portions of the conductive cap to be
contacted with the terminal electrodes when the conductive cap is
fixed to the surface of the substrate. The conductive cap alone can
be fixed to the surface of the substrate by an adhesive or other
joining material or element to achieve sealing.
[0044] As the electrodeposition according another preferred
embodiment of the present invention, a conventional generally-used
electrodeposition coating method can be adopted. The
electrodeposition coating can be performed by use of a cationic or
anionic electrodeposition coating material and by setting the
conductive cap as a cathode or anode.
[0045] Preferably, a conductive double side adhesion tape is bonded
to a conductive supporting sheet, and the metallic cap is bonded to
the conductive double side adhesion tape, electrically connected,
supported, and electrodeposition-coated. According to this method,
many conductive caps can be simultaneously bonded to the double
side adhesion tape to be supported and fixed. Thus, many metallic
caps can be electrodeposition coated simultaneously and
efficiently.
[0046] Also preferably, the electrodeposition-coating is carried
out while the conductive cap is supported by a jig, and
electrically connected. According to this method, the cap can be
held and fixed by the simple jig.
[0047] According to a further preferred embodiment of the present
invention, there is provided a conductive cap for sealing an
electronic component, which is fixed to the surface of the
substrate of the electronic component having terminal electrodes
disposed thereon so as to cover and seal an element mounted onto
the surface of the substrate, wherein an insulating film-is formed
at least on the portions of the conductive cap to be contacted with
the terminal electrodes by electrodeposition coating.
[0048] Other features, characteristics, elements and advantages of
the present invention will become apparent from the following
description of preferred embodiments thereof with reference to the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1A is a cross-sectional view showing an electronic
component having a cap according to a preferred embodiment of the
present invention;
[0050] FIG. 1B is a fragmentary enlarged sectional view showing the
essential component of the electronic component of FIG. 1A;
[0051] FIG. 2A is a perspective view showing a conductive cap
included in the electronic component having a cap according to a
preferred embodiment of the present invention;
[0052] FIG. 2B is a cross-sectional end view taken along line A-A
of FIG. 2A;
[0053] FIG. 2C is a bottom view of the conductive cap of FIG.
2A;
[0054] FIG. 3 is a bottom view showing a conductive cap held by a
holding device in a preferred embodiment of the present
invention;
[0055] FIG. 4 is a cross-sectional view illustrating a process of
forming an insulating film on a conductive cap by a transfer
method;
[0056] FIG. 5A is a perspective view of a conductive cap according
to another preferred embodiment of the present invention;
[0057] FIG. 5B is a sectional end surface view taken along line A-A
of FIG. 5A;
[0058] FIG. 5C is a bottom view of the conductive cap of FIG.
5A;
[0059] FIG. 6 is a perspective view illustrating an example of a
conventional electronic component having a cap;
[0060] FIG. 7 is a longitudinal cross-sectional view showing an
example of a conventional chip piezoelectric resonation
portion;
[0061] FIG. 8 is a cross-sectional view showing an example of an
electronic component using a metallic cap having an insulating film
formed according to preferred embodiments of the present
invention;
[0062] FIG. 9A is a perspective view showing a metallic cap
according to another preferred embodiment of the present
invention;
[0063] FIG. 9B is a cross-sectional view taken along line A-A of
FIG. 9A;
[0064] FIG. 9C is a bottom view of the metallic cap of FIG. 9A;
[0065] FIG. 10A is a perspective view of a metallic cap according
to a further preferred embodiment of the present invention;
[0066] FIG. 10B is a cross-sectional view taken along line A-A of
FIG. 10A;
[0067] FIG. 11C is a bottom view of the metallic cap of FIG.
10A;
[0068] FIG. 11A is a perspective view of a metallic cap according
to a still further preferred embodiment of the present
invention;
[0069] FIG. 11B is a cross-sectional view taken along line A-A of
FIG. 11A;
[0070] FIG. 11C is a bottom view of the metallic cap of FIG.
11A;
[0071] FIG. 12A is a perspective view of a metallic cap according
to another preferred embodiment of the present invention;
[0072] FIG. 12B is a cross-sectional view taken along line A-A of
FIG. 12A;
[0073] FIG. 12C is a bottom view of the metallic cap of FIG.
12A;
[0074] FIG. 13A is a perspective view of a metallic cap according
to yet another preferred embodiment of the present invention;
[0075] FIG. 13B is a cross-sectional view taken along line A-A of
FIG. 13A;
[0076] FIG. 13C is a bottom view of the metallic cap of FIG.
13A;
[0077] FIG. 14 is a cross-sectional view illustrating the metallic
cap when it is anodization-treated according to a preferred
embodiment of the present invention;
[0078] FIG. 15 is a perspective view illustrating a further
preferred embodiment of the present invention;
[0079] FIG. 16 is a cross-sectional view illustrating a still
further preferred embodiment of the present invention;
[0080] FIG. 17 is a front view illustrating another preferred
embodiment of the present invention;
[0081] FIG. 18 is a cross-sectional view showing the state in which
connection portions between a metallic cap in a hoop are provided
with a cut-in, respectively;
[0082] FIG. 19 is a cross-sectional view showing the state in which
the hoop shown in FIG. 18 has been anodized;
[0083] FIG. 20 is a cross-sectional view showing an example of a
conventional electronic component;
[0084] FIG. 21 is a perspective view showing an example of a
conventional electronic component;
[0085] FIG. 22 is a cross-sectional view showing an example of an
electronic component using a metallic cap having an insulating film
formed according to preferred embodiments of the present
invention;
[0086] FIG. 23A is a perspective view showing a metallic cap
according to a preferred embodiment of the present invention;
[0087] FIG. 23B is a cross-sectional view taken along line A-A in
FIG. 23A;
[0088] FIG. 23C is a bottom view thereof according to FIG. 23A;
[0089] FIG. 24A is a perspective view showing a metallic cap
according to a further preferred embodiment of the present
invention;
[0090] FIG. 24B is a cross-sectional view taken along line A-A in
FIG. 24A;
[0091] FIG. 24C is a bottom view of the metallic cap of FIG.
24A;
[0092] FIG. 25A is a perspective view showing a metallic cap
according to still a further preferred embodiment of the present
invention;
[0093] FIG. 25B is a cross-sectional view taken along line A-A in
FIG. 25A;
[0094] FIG. 25C is a bottom view of the metallic cap of FIG.
25A;
[0095] FIG. 26A is a perspective view showing a metallic cap
according to another preferred embodiment of the present
invention;
[0096] FIG. 26B is a cross-sectional view taken along line A-A in
FIG. 26A;
[0097] FIG. 26C is a bottom view of the metallic cap of FIG.
26A;
[0098] FIG. 27A is a perspective view showing a metallic cap
according to yet another preferred embodiment of the present
invention;
[0099] FIG. 27B is a cross-sectional view taken along line A-A in
FIG. 27A;
[0100] FIG. 27C is a bottom view of the metallic cap of FIG.
27A;
[0101] FIG. 28 is a front view illustrating the state in which
metallic caps are supported according to a preferred embodiment of
the present invention;
[0102] FIG. 29 is a cross-sectional view further illustrating the
state of FIG. 28 in which the metallic caps are supported;
[0103] FIG. 30 is a front view illustrating the state in which
metallic caps are supported according to a further preferred
embodiment of the present invention;
[0104] FIG. 31 is a cross-sectional view further illustrating the
state of FIG. 30 in which the metallic caps are supported; and
[0105] FIG. 32 is a cross-sectional view in which metallic caps are
supported according to still a further preferred embodiment of the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0106] FIG. 1A is a cross-sectional view of an electronic component
according to a preferred embodiment of the present invention. FIG.
1B is a fragmentary sectional view showing the essential portion of
the electronic component shown in FIG. 1A.
[0107] The package of an electronic component with a cap 101
preferably includes a substrate 102 and a metallic cap 103 that
defines a conductive cap. A piezoelectric element 4 is accommodated
in the package.
[0108] The substrate 102 is preferably made of insulating ceramic
such as alumina or other suitable material, and preferably has a
substantially rectangular shape. The substrate 102 may be made of
another insulating material such as synthetic resin or other
suitable.
[0109] Terminal electrodes 105 and 106 are arranged to extend from
the upper surface 102a of the substrate 102 onto the lower surface
102d via the end surfaces 102b and 102c, respectively. The
above-mentioned piezoelectric element 104 is fixed to the upper
surface 102a of the substrate 102 by conductive bonding agents 107
and 108 such as solder or other suitable material. The conductive
bonding agents 107 and 108 also electrically connect the electrodes
(not shown) of the piezoelectric element 104 to the terminal
electrodes 105 and 106, respectively.
[0110] As the piezoelectric element 104, an element utilizing an
appropriate piezoelectric effect such as a piezoelectric resonator,
a piezoelectric filter, or other suitable element may be
included.
[0111] In order to seal the piezoelectric element 104, a metallic
cap 103 is bonded to the upper surface 102a of the substrate 102 by
an insulating adhesive (not shown). The metallic cap 103 has an
opening 103a at the lower portion thereof. An insulating film 109
is provided on the end surface 103b of the opening, and on the
portions of the inner surface 103c and the outer surface 103d in
connection to and in the vicinity of the opening end surface
103b.
[0112] A metallic material for forming the metallic cap 103 has no
limitations. For example, aluminum, stainless steel, and so forth
may be used.
[0113] The metallic cap 103 preferably has a substantially
rectangular shape, as shown in FIGS. 2A, 2B, and 2C. The metallic
cap 103 can be simply obtained by forming a sheet metallic
material. Further, the insulating film 109 is formed on the
metallic cap 103 according to a method described later.
[0114] One of the characteristics of the electronic component 101
of this preferred embodiment is how the insulating film 109 is
formed on the metallic cap 103. The structure of the portion of the
metallic cap 103 where the insulating film 109 is formed will be
described in detail with reference to FIG. 1B.
[0115] When the portion of the metallic cap 103 near to the opening
is viewed in section taken perpendicularly relative to the
circumferential direction of the opening 103a of the metallic cap
103, as shown in FIG. 1B, the opening end surface 103b of the
metallic cap 103 to be bonded to the terminal electrode 105 and 106
of the metallic cap 103, and the inner-side surface 103c in
connection to the opening end surface 103b define a curved line.
The radius R of curvature of the curved line is preferably in the
range of about 80 .mu.m to about 150 .mu.m. The insulating film 109
is formed on the opening end surface 103b, and portions of the
inner-side surface 103c and the outer-side surface 103d in the
vicinity of the opening end surface 103b.
[0116] The insulating film 109 may be made of appropriate
insulating materials. Preferably, an insulating resin capable of
being melted and coated is used to form the insulating film 109
because of the resultant advantages in the production process
described later. More preferably, as the insulating resin, a resin
having a heat resistance that is durable to heat generated when the
electronic component having the cap is mounted onto a printed
circuit board by a reflow-soldering method. Further, preferably,
the insulation resistance of the insulating film 109 is about
10.sup.9 .OMEGA. or higher.
[0117] When an appropriate insulating synthetic resin such as epoxy
resin, polyimide resin, or other such material is used as material
for forming the insulating film 109, the thickness of the
insulating film 109 preferably about 4 .mu.m or more so that the
insulation resistance becomes about 10.sup.9 .OMEGA. or higher. If
the thickness of the insulating film 109 is less than about 4
.mu.m, the insulation resistance is reduced, and probably, the
reliability is deteriorated. The insulating film 109 is not
especially restricted to the upper limit from the viewpoint of
securing the insulation resistance. However, if the thickness
exceeds about 25 .mu.m, the thickness of the insulating film
adhering to the opening end surface 103b of the metallic cap 103
and the side surfaces 103c and 103d in connection to the opening
end surface 103b becomes large, the inner size of the metallic cap
103 becomes small, and the outer dimension thereof becomes larger.
Accordingly, it is necessary to prepare a large substrate 102, and
moreover, the size of the piezoelectric element 104 to be
accommodated has a limitation.
[0118] Desirably, the opening end surface 103b of the metallic cap
103, and the inner-side surface 103c in connection to the opening
end surface 103b are arranged so that the radius R of curvature
shown in FIG. 1B is in the range of about 80 .mu.m to about 150
.mu.m, as described above. If the radius R of curvature is less
than about 80 .mu.m, the contact areas between the metallic cap 103
and the terminal electrodes 105 and 106 on the substrate 102 are
reduced. This may deteriorate the reliability with which the
metallic cap 103 is bonded to the substrate 102. Further, the
insulating film 109 is difficult to adhere to the metallic cap 103,
so that the insulating layer 109 having a sufficient thickness is
difficult to form. On the other hand, if the radius R of curvature
exceeds about 150 .mu.m, metallic burrs or edges are readily formed
on the opening end surface 103b of the metallic cap 103, which
makes the insulating film 109 difficult to adhere to the opening
end surface 103b.
[0119] Desirably, the insulating resin for forming the
above-described insulating film 109 has a melt-viscosity suitable
for coating onto the metallic cap 103. Preferably, a resin having a
viscosity at a temperature of about 25.+-.5.degree. C. of about
5000 cps to about 20000 cps is preferably used. For a resin having
a viscosity of less than about 5000 cps, an insulating film having
a sufficient film thickness is formed from the resin with much
difficulty, if it is applied by a transfer method, and unless the
number of transfer cycles is increased. In order to attain an
insulating film 109 having an appropriate thickness, it is
desirable that the thickness is not less than about 5000 cps. On
the other hand, if the viscosity exceeds about 20000 cps, the
thickness of the insulating film 109 formed by transfer-processing
one time becomes excessively thick, causing problems similar to
those of the case where the thickness of the insulating film 109
exceeds about 25 .mu.m.
[0120] Next, a method of forming the insulating film 109 on the
metallic cap 103 will be described with reference to FIGS. 3 and
4.
[0121] According to this method, a supporting device 111 is
prepared as shown in the bottom view of FIG. 3. A rubber layer 111a
having pressure sensitive adhesive properties is provided on the
lower surface of the supporting device 111. The rubber layer 111a
having pressure-sensitive adhesive properties is preferably made of
an appropriate silicone or acryl type of pressure-sensitive
adhesive.
[0122] A plurality of metallic caps 103 are bonded to the
pressure-sensitive adhesive rubber layer 111a. The top surfaces of
the respective metallic caps 103 are bonded to the rubber layer
111a, respectively.
[0123] The plurality of metallic caps 103 are preferably arranged
in a matrix as shown in FIG. 3.
[0124] In order to bond the plurality of metallic caps 103 to the
supporting device 111, the plurality of metallic caps 103 are
preferably arranged in a matrix and placed on a stage (not shown)
beforehand. The rubber layer 111a of the supporting device 111 is
lowered from above the metallic caps 103 and is contacted with the
top surfaces of the metallic caps 3.
[0125] After this, the metallic caps 103 supported on the
supporting device 111 are lowered toward an insulation film
formation stage 112, as shown in FIG. 4. On the upper surface 112a
of the insulating film formation stage 112, an insulating resin
layer 109A is provided. The insulating resin layer 109A is formed
by melting and coating a resin to form the above-mentioned
insulating film 109. The insulating resin layer 109A has not been
dried yet and is conditioned to have a viscosity at about
25.+-.5.degree. C. in the range of about 5000 cps to about 20000
cps.
[0126] Accordingly, the opening surfaces 103a of the metallic caps
103 supported on the supporting device 111 are contacted with the
insulating resin layer 109A, and thereafter, the metallic caps 103
are lifted, whereby the insulating resin is coated on the
circumferential edge of the opening 103a of each metallic cap 103.
After this, the coated insulating resin is dried to define the
above-mentioned insulating film 109.
[0127] According to the method of forming an insulating film of
this preferred embodiment, the insulating film 109 can be securely
and simply formed on the plural metallic caps 103 by the transfer
method. Preferably, the transfer process is carried out several
times. That is, even if pinholes are formed in the insulating film
109 formed by transferring one time, short-circuiting between the
metallic caps 103 and the terminal electrodes 105 and 106, caused
by the pinholes, can be securely prevented by repeating the
transfer process many times.
[0128] After the insulating film 109 is formed on the metallic caps
103 as described above, the metallic caps 103 are bonded to the
substrate 102 having a piezoelectric element mounted thereto by an
insulating adhesive. In this case, the insulating adhesive is
coated on the circumferential edge of the opening of each metallic
cap 103. The metallic caps 103 are bonded to the substrate 102 one
by one. This is because each piezoelectric element 4 must be
securely sealed within the package in the process of bonding the
metallic caps 103 to the substrate 102 by the insulating adhesive,
and therefore, the bonding process are carried out with high
precision.
[0129] In particular, in the transfer process of forming the
insulating film 109 not requiring such a high precision, the
plurality of metallic caps 103 can be processed one time and
simultaneously as described above. On the other hand, in the
process of bonding the metallic caps 103 to the substrate 102, the
plurality of metallic caps 103 can not be bonded to the substrate
102 at the same time. In other words, in the process of forming the
insulating film 109 by the above-described transfer method, the
insulating film 109 can be formed easily and efficiently, since the
plurality of metallic caps 103 can be processed at the same
time.
[0130] The process of bonding the metallic caps 103 to the upper
side of the substrate 102 by the insulating adhesive may be carried
out according to a conventional method such as that disclosed in
Japanese Unexamined Patent Application Publication No. 11-121916
and Japanese Unexamined Patent Application Publication No.
11-126961.
[0131] In the above-described preferred embodiment, the insulating
film 109 is provided on the opening end surface 103b of each
metallic cap 103 and the vicinity thereof. According to the method
of producing a conductive cap of preferred embodiments of the
present invention, the insulating film may be formed on the upper
surface 103e of the metallic cap 103. That is, the insulating film
109b may be formed on the upper surface 103e of the metallic cap
103, as shown in FIGS. 5A, 5B, and 5C. By forming the insulating
film 109b on the upper surface 103e of the metallic cap 103,
short-circuiting caused by the contact between the conductive
component 101 having a cap and other elements or wires can be
securely prevented.
[0132] In the above-described preferred embodiment, as the
electronic component having a cap, a chip piezoelectric resonance
component having the piezoelectric element 104, as shown in FIG. 4,
accommodated therein is illustrated as an example. Various
preferred embodiments of the present invention may be applied to an
appropriate electronic component having a cap in which an
electronic component element is accommodated in the package
including a substrate and the conductive cap. That is, as the
electronic component element, an electronic component element other
than the piezoelectric element may be used.
[0133] Further, as the conductive cap, the metallic cap 3 is
described, but the present invention is not limited thereto. A
conductive cap produced by forming a conductive film on the surface
of a cap made of an insulating material such as insulating ceramic,
e.g., alumina, and synthetic resin, and other suitable material may
be used, for example.
[0134] FIG. 8 is a cross-sectional view showing an electronic
component provided with a metallic cap having an insulating film
disposed thereon according to a preferred embodiment of the present
invention.
[0135] Terminal electrodes 11 and 12 are provided on the end
surfaces, the upper surface, and the lower surface in the opposite
end-portions of a substrate 10 such as a dielectric substrate or
other suitable substrate. Further, a terminal electrode 13 is
provided at the approximate center of the lower surface of the
substrate 10. Capacitors are defined between the terminal
electrodes 11 and 13 and between the terminal electrodes 12 and 13.
Another capacitor is defined between the terminal electrodes 11 and
12. Moreover, internal electrodes may be provided in the substrate
10 so as to be contacted with the terminal electrodes 11 and 12. A
capacitor may be produced between these internal electrodes.
[0136] An element 20 such as a piezoelectric resonation element or
other suitable element is mounted on the upper surface of the
substrate 10. One end of the element 20 is bonded to the terminal
electrode 11 by solder 21, and the other end is bonded to the
terminal electrode 12 with solder 22. Further, a metallic cap 1 is
fixed to the upper surface of the substrate 10 so as to cover and
seal the element 20. The metallic cap 1 is preferably made of
aluminum or an alloy thereof. An insulating film 2 is provided on
the surface of the metallic cap 1. The insulating film 2 is formed
by anodization of the surface of the metallic cap 1. The thickness
of the insulating film 2 is preferably in the range of about 3
.mu.m to about 30 .mu.m.
[0137] The insulating film 2 is interposed between the terminal
electrodes 11, 12 and the metallic cap 1, as shown in FIG. 8.
Hence, the metallic cap 1 is prevented from directly contacting the
terminal electrodes 11 and 12, that is, sufficient insulation can
be maintained between terminal electrodes 11, 12. The metallic cap
1 may be bonded to the substrate 10 by an appropriate adhesive or
other suitable joining material or member.
[0138] FIGS. 9A, 9B, and 9C to FIG. 13A, 13B, and 13C show examples
of the area in the surface of each metallic cap where the
insulating film is formed. FIGS. 9A to 13A are perspective views of
the metallic caps, respectively. FIGS. 9B to 13B are
cross-sectional views taken along lines A-A in FIGS. 9A to 13A,
respectively. FIGS. 9C to 13C show the bottoms of the metallic
caps, namely, the surfaces thereof to be contacted with substrates,
respectively. In the respective figures, the area where the
insulating film is provided is shown cross-hatched.
[0139] As shown in FIGS. 9A-9C, the insulating film 2 may be
arranged to extend along the entire surface of the metallic cap 1.
In the preferred embodiment of FIGS. 9A-9C, the insulating film 2
is disposed on the whole of the outer surface of the metallic cap
1, the inner surface, and the bottom to be contacted with the
substrate when the metallic cap 1 is fixed to the substrate. By
forming the insulating film 2 on the entire surface of the metallic
cap 1, the electrical insulation is maintained, and the electrical
characteristics of the electronic component are prevented from
being deteriorated, when the electronic component is mounted onto a
circuit board, even if the electronic component contacts other
elements. In addition, the insulating film 2 is disposed on the
inner surface of the metallic cap 1. Hence, the insulation between
the elements and solders or other elements located inside of the
metallic cap 1 is maintained.
[0140] In the preferred embodiment of FIG. 10, the insulating film
2 is disposed on the surface of the metallic cap 1 excluding the
outer upper surface thereof. When no insulating film is formed on
the upper surface of the metallic cap 1, as described above, the
insulation between the metallic cap and the terminal electrodes can
be checked by utilization of the upper surface of the metallic cap
1 .
[0141] In the preferred embodiment of FIG. 11, the area where no
insulating film 2 is formed is provided in the approximate center
of each side surface of the metallic cap 1. Also the area where no
insulating film is formed is extended onto the bottom surface of
the metallic cap 1. Care should be taken so that the area where the
insulating film is formed does not contact the terminal electrodes.
Such an insulating film pattern of the metallic cap can be formed
e.g., in the anodization of a hoop material as described later. By
connecting a ground to the area where no insulating film 2 is
formed, the metallic cap 1 provides a shielding function.
[0142] In the preferred embodiment of FIG. 12, the area where no
insulating film 2 is formed is provided at the approximate center
of each side surface of the metallic cap. Also, this metallic cap 1
can provide a shielding function by connecting a ground to the area
where no insulating film 2 is formed.
[0143] In the preferred embodiment of FIG. 13, the insulating film
2 is provided only on the lower end-portion of the metallic cap 1.
That is, the insulating film 2 is disposed on the lower end
portions on the outer side and the inner side of the metallic cap 1
and on the bottom thereof. Also the metallic cap 1 can provide a
shielding function by connecting a ground to the area where no
insulating film 2 is formed.
[0144] As described above, according to a preferred embodiment of
the present invention, the area where no insulating film is formed
has no limitation. The insulating film only has to be provided on
the surfaces of the metallic cap so as to contact the terminal
electrodes.
[0145] FIG. 14 is a cross-sectional view illustrating a method of
forming an insulating film according to a preferred embodiment of
the present invention. In this preferred embodiment, a metallic cap
1 is electrically connected while the cap 1 is held by a jig 3, set
as an anode, and anodized. As the jig 3, a metallic spring piece
capable of fixing the metallic cap 1 on the inside thereof may be
used. The anodization as described above is suitable when the
metallic caps 1 are separated and discrete from each other.
[0146] FIG. 15 is a perspective view illustrating anodization
according to another preferred embodiment of the present invention.
In this preferred embodiment, caps 1 are connected to each other in
a hoop 4. The hoop 4 is obtained after a sheet material is punched
and formed into cap shapes and before the caps 1 are removed from
the punched potions of the hoop 4. In order to electrically connect
the metallic caps 1 in the hoop 4, for example, a conduction roll 5
shown in FIG. 15 is contacted with the hoop 4.
[0147] FIG. 16 shows an example of continuously anodizing the hoop
4 of FIG. 15. The hoop 4 is wound around a feeding roll 6, and fed
from the roll 6 to an anodization bath 8. The hoop 4 is contacted
with the conduction roll 5 and is in electrical conduction. In the
anodization bath 8, the metallic caps 1 are anodized, whereby an
oxidized film is formed on the caps 1. The hoop 4, after the
anodization, is wound around a take-up roll 7. Thus, the metallic
caps 1 in the hoop 4 can be continuously anodized.
[0148] FIG. 17 is a front view illustrating anodization according
to a further preferred embodiment of the present invention. In this
preferred embodiment, the hoop 4 cut to a predetermined unit length
is used. The cut hoop 4 is dipped in an anodization bath and
anodized. That is, the hoop 4 is anodized by a batch system. The
hoop 4 is held by a holding device 9 under electrical conduction,
and in this state, is dipped into the anodization bath, so that an
insulating film made of an oxidized film is formed on the surface
of the caps.
[0149] After the anodization is carried out in the hoop state as
described above, the metallic caps 1 are removed from the hoop 1.
In this case, the metal caps 1 are cut off from the hoop 4 at the
connection portions in the hoop 4. No insulating film is formed in
the cut-off portions. Accordingly, a metallic cap having an
insulating film pattern as shown in FIG. 11 can be produced.
[0150] FIG. 18 is a cross-sectional view showing cuts 4a and 4b
provided in the connection portion between the metallic cap 1 and
the hoop 4. By providing the cuts 4a and 4b to reduce the thickness
of the connection portion, the metallic cap can be easily removed
from the hoop 4 after the anodization.
[0151] FIG. 19 shows the state in which the anodization has been
carried out. As shown in FIG. 19, insulating films 2, which are
oxidized films, are formed on the front and back surfaces of the
hoop 4. The insulating film 2 has a uniform thickness disposed over
the hoop 4. In the portions where the cuts are 4a and 4b are
formed, the thickness of the metallic sheet becomes very small.
Accordingly, the metallic caps 1 can be removed by applying a small
external force.
[0152] The cuts 4a and 4b shown in FIG. 18 may be formed so as to
have a depth that is substantially equal to about a half the
thickness of the metallic sheet.
[0153] In the above-described preferred embodiments, as the
substrate for mounting an element, a substrate such as a dielectric
substrate or other suitable substrate is described. The present
invention is not restricted to the dielectric substrate. For
example, an insulating substrate or other substrate may be
included.
[0154] FIG. 22 is a cross-sectional view showing an electronic
component provided with a metallic cap having an insulating film
formed thereon according to a preferred embodiment of the present
invention.
[0155] Terminal electrodes 11 and 12 are formed on the end
surfaces, the upper surface, and the under surface in the opposite
end-portions of a substrate 10 such as a dielectric substrate or
other suitable substrate. Further, a terminal electrode 13 is
provided at the approximate center of the lower surface of the
substrate 10. Capacitors are defined between the terminal
electrodes 11 and 13 and between the terminal electrodes 12 and 13.
Another capacitor is defined between the terminal electrodes 11 and
12. Moreover, internal electrodes may be provided in the substrate
10 so as to be contacted with the terminal electrodes 11 and 12. A
capacitor may be defined between these internal electrodes.
[0156] An element 20 such as a piezoelectric resonation element or
other electronic element is mounted onto the upper surface of the
substrate 10. One end of the element 20 is bonded to the terminal
electrode 11 by solder 21, and the other end is bonded to the
terminal electrode 12 with solder 22. Further, a metallic cap 1 is
fixed to the upper surface of the substrate 10 so as to cover and
seal the element 20. The metallic cap 1 is preferably made of
aluminum or an alloy thereof. An insulating film 2 is disposed on
the surface of the metallic cap 1. The insulating film 2 is formed
by anodization of the surface of the metallic cap 1. The thickness
of the insulating film 2 is preferably in the range of about 3
.mu.m to about 30 .mu.m.
[0157] The insulating film 2 is interposed between the terminal
electrodes 11, 12 and the metallic cap 1, as shown in FIG. 22.
Hence, the metallic cap 1 is prevented from directly contacting
with the terminal electrodes 11 and 12, that is, sufficient
insulation can be maintained between the terminal electrodes 11,
12. The metallic cap 1 may be bonded to the substrate 10 by an
appropriate adhesive or other suitable joining material or
member.
[0158] FIGS. 23A, 23B, and 23C to FIG. 27A, 27B, and 27C show
examples of the area in the surface of each metallic cap where the
insulating film is formed. FIGS. 23A to 27A are perspective views
of the metallic caps, respectively. FIGS. 23B to 27B are
cross-sectional views taken along lines A-A in FIGS. 23A to 27A,
respectively. FIGS. 23C to 27C show the bottoms of the metallic
caps which are the surfaces thereof to be contacted with
substrates, respectively. In the respective figures, the area where
the insulating film is provided is cross-hatched.
[0159] As shown in FIG. 23, the insulating film 2 may be arranged
along the entire surface of the metallic cap 1. In the preferred
embodiment of FIG. 9, the insulating film 2 is disposed on the
entire outer surface of the metallic cap 1, the inner surface, and
the bottom to be contacted with the substrate when the metallic cap
1 is fixed to the substrate. By forming the insulating film 2 on
the entire surface of the metallic cap 1, the electrical insulation
can be maintained, and the electrical characteristics of the
electronic component can be prevented from being deteriorated, when
the electronic component is mounted onto a circuit board, even if
the electronic component contacts with other elements. In addition,
the insulating film 2 is formed on the inner surface of the
metallic cap 1. Hence, the insulation between the elements and
solders or other elements located inside of the metallic cap 1 can
be maintained.
[0160] In the preferred embodiment of FIG. 24, the insulating film
2 is provided on the surface of the metallic cap 1 excluding the
outer upper surface thereof. In the case where no insulating film
is formed on the upper surface of the metallic cap 1, as described
above, the insulation between the metallic cap and the terminal
electrodes can be checked by utilization of the upper surface of
the metallic cap 1.
[0161] In the preferred embodiment of FIG. 25, the area where no
insulating film 2 is formed is provided at the approximate center
of each side surface of the metallic cap 1. Also the area where no
insulating film is formed is extended onto the lower surface of the
metallic cap 1. Care should be taken so that the area where no
insulating film is formed does not contact the terminal electrodes.
Such an insulating film pattern of the metallic cap can be formed
e.g., in the anodization of a hoop material as described later. By
connecting a ground to the area where no insulating film 2 is
formed, the metallic cap 1 can provide a shielding function.
[0162] In the preferred embodiment of FIG. 26, the area where no
insulating film 2 is formed is provided in the approximate center
of each side surface of the metallic cap. Also, this metallic cap
can provide a shielding function by connecting a ground to the area
where no insulating film is formed.
[0163] In the preferred embodiment of FIG. 27, the insulating film
2 is formed only on the lower end-portion of the metallic cap 1.
That is, the insulating film 2 is formed on the lower end portions
on the outer side and the inner side of the metallic cap 1 and on
the bottom thereof. Also the metallic cap 1 can provide a shielding
function by connecting a ground to the area where no insulating
film 2 is formed.
[0164] As described above, according to preferred embodiments of
the present invention, the area where no insulating film is formed
has no limitation. The insulating film only has to be provided on
the surfaces of the metallic cap to be contacted to the terminal
electrodes.
[0165] FIG. 28 is a cross-sectional view illustrating a method of
forming an insulating film according to a first preferred
embodiment of the present invention. A conductive double-side
adhesion tape 31 is bonded to a conductive support sheet 30 made of
a metallic sheet or other suitable material. The conductive
double-side adhesion tape 31 has conductive properties by
incorporating, e.g., metallic powder, carbon black, or other
suitable material therein. A plurality of metallic caps 1 are
bonded to the conductive double side adhesion tape 31. The
conductive support sheet 30 is supported by a conductive support 32
made of metal or other suitable material.
[0166] FIG. 29 is a cross-sectional view showing the metallic caps
1 of FIG. 28 in a supported state. As seen in FIG. 29, the upper
sides of the metallic caps 1 are bonded to the conductive double
side tape 31. The metallic caps 1 are electrically conducted to the
conductive support sheet 30 via the conductive double side adhesion
tape 31. Hence, by setting the conductive support sheet 30 as a
cathode or an anode via the support 32, the metallic caps 1 can be
made to function as a cathode or anode.
[0167] By dipping the metallic caps 1 supported as described above,
into an electrodeposition coating material, and setting the
metallic caps 1 as a cathode or anode, the material can be
electrodeposition-coated onto the exposed surface of the metallic
caps 1. That is, an insulating film can be formed by the
electrodeposition coating. According to the supporting method of
this preferred embodiment, the upper surfaces of the metallic caps
1 are bonded to the conductive double side adhesion tape 31.
Accordingly, no insulating film is formed on the upper surfaces of
the metallic caps 1. Accordingly, the same insulating film pattern
as in the example shown in FIG. 3 can be formed.
[0168] FIG. 30 is a front view showing a method of forming an
insulating film according to another preferred embodiment of the
present invention. FIG. 31 is a cross-sectional view showing the
supported state of the metallic caps of FIG. 30.
[0169] Referring to FIGS. 30 and 31, protuberances 33a elongating
in the lateral direction are disposed on a conductive support sheet
33 made of a metallic sheet or other suitable material, as shown in
FIG. 31. Conductive double side adhesion tapes are bonded to the
protuberances 33a, respectively. The conductive double bond
adhesion tapes have conductive properties by incorporating e.g.,
metallic powder, carbon black, or other suitable material similarly
to the conductive double bond adhesion tape 31 shown in FIGS. 28
and 29. The metallic caps 1 are bonded to the conductive double
bond adhesion tapes 34, respectively. As shown in FIG. 31, the
bottom of each metallic cap 1 is bonded to the conductive double
bond adhesion tape 34. The conductive support sheet 33 is held by a
conductive holding device 35 made of metal or other suitable
material.
[0170] Each metallic cap 1 is electrically connected to the
conductive support sheet 33 via the conductive double bond adhesion
tape 34. Accordingly, by setting the conductive supporting sheet 33
as a cathode or anode, the metallic cap 1 can be made to function
as a cathode or anode. Hence, by dipping the metallic caps 1
supported as described above in an electrodeposition coating
material, and setting the metallic caps 1 as a cathode or anode,
the material can be electrodeposition-coated onto the surfaces of
the metallic caps 1.
[0171] The electrodeposition coating has good coating performance.
Not only the outer surface of each metallic cap 1 but also the
inner surface thereof can be coated. However, the portion of the
metallic cap 1 in contact with the conductive double bond adhesion
tape 34 is not coated. Thus, no coating film is formed on the
approximate center portion of the bottom of the metallic cap 1.
Accordingly, the insulating film pattern on the bottom of the
metallic cap 1 is similar to that shown in FIG. 25C. Care should be
taken so that the areas where no insulating film is formed do not
overlap the areas of the terminal electrodes.
[0172] FIG. 32 is a cross-sectional view showing a method of
forming an insulating film according to another preferred
embodiment of the present invention. In this preferred embodiment,
spring members 37 made of a conductive material such as metal or
other suitable material are provided. The metallic cap 1 is pushed
between the spring members 37 to be supported. The metallic cap 1
is electrically connected to the conductive supporting sheet 36 via
the spring members 37. Accordingly, by setting the conductive
supporting sheet 36 as a cathode or anode, the metallic cap 1 can
be made to function as a cathode or anode.
[0173] By dipping the metallic caps 1 supported as described above
into an electrodeposition coating material, and setting the
metallic caps 1 as a cathode or anode, an insulating film made of
an electrodeposition coating film can be formed on the exposed
surfaces of the metallic caps 1. In this preferred embodiment, the
insulating film can be formed on the surface of each metallic cap 1
excluding the surface portion of the metallic cap 1 in contact with
the spring member 37.
[0174] As described above, according to various preferred
embodiments of the present invention, the insulating film can be
formed in the shaped-cap state. Thus, it is unnecessary to form the
insulating film, and then carry out bending-work or other
conventional processes. A very good insulating film can be formed
on the surface portions of the cap to be contacted with the
terminal electrodes.
[0175] In the above-described preferred embodiments, as the
substrate for mounting an element, a substrate such as a dielectric
substrate or other suitable substrate may preferably be used as an
example. The present invention is not limited to the preferred
embodiments described above. For example, an insulating substrate
or other substrate may be used.
[0176] In the conductive cap of preferred embodiments of the
present invention, the end surface of the opening on the lower
surface of the cap and the inner and outer side surfaces thereof in
connection to and in the vicinity of the end surface is provided
with an insulating film disposed thereon. Hence, in the case where
the conductive cap is bonded to the upper surface of the substrate
having terminal electrodes formed thereon by an insulating
adhesive, the conductive cap and the terminal electrodes can be
securely prevented from short-circuiting.
[0177] Regarding a conventional electronic component having a cap
in which an insulating film is formed on the substrate, it becomes
difficult to form the insulating film with high precision as the
electronic component becomes more miniaturized. This prevents the
size of the electronic component from being reduced. On the other
hand, when the conductive cap of preferred embodiments of the
present invention is used, it is unnecessary to form an insulating
film on the substrate. Thus, the conductive cap can sufficiently
correspond to the miniaturization.
[0178] The insulation resistance between the opening end surface of
the conductive cap and the outer side of the insulation film may be
at least about 10.sup.9 .OMEGA.. In this case, short-circuiting
between the conductive cap and the terminal electrodes on the
substrate is prevented more securely.
[0179] Further, the thickness of the insulating film is preferably
in the range of about 4 .mu.m to about 25 .mu.m. In this case, the
electrical insulation between the conductive cap and the terminal
electrodes can be securely performed, the substrate can be
prevented from increasing in size, and moreover, limitations in
size of an electronic component element to be accommodated can be
reduced.
[0180] Preferably, when the opening end surface of the conductive
cap and its adjacent portion thereof are viewed in a section taken
perpendicularly relative to the circumferential direction of the
conductive cap, the opening end surface of the cap and the inner
side surface thereof connected to the opening end surface define a
curved line, and the radius R of curvature of the curved line is
preferably in the range of about 80 .mu.m to about 150 .mu.m. In
this case, the insulating film having a sufficient thickness can be
securely provided on the opening end surface and the vicinity
thereof, and thereby, short-circuiting between the terminal
electrodes and the conductive cap can be securely prevented.
[0181] In the electronic component of various preferred embodiments
of the present invention, an electronic component element is fixed
to the substrate and electrically connected to the plurality of
terminal electrodes on the substrate, and the opening side of the
conductive cap according to various preferred embodiments of the
present invention is bonded to the substrate so as to cover the
electronic component element. Thus, short-circuiting between the
conductive cap and the terminal electrodes is securely prevented
due to the insulating film disposed on the conductive cap.
[0182] In the electronic component of preferred embodiments of the
present invention, the electronic component element may be a
piezoelectric element. In this case, short-circuiting between the
conductive cap and the terminal electrodes on the substrate can be
securely prevented. As a result, a piezoelectric component having
very high reliability is provided.
[0183] In the case where the conductive cap is made of a metallic
cap, the conductive cap can be easily formed from a sheet metallic
material by drawing or other suitable process.
[0184] According to the method of forming an insulating film of an
conductive cap of a preferred embodiment of the present invention,
a plurality of conductive caps are held while they are arranged by
a holding device, the opening end surface side of the plurality of
conductive caps held by the holding device are pressed against a
resin layer for forming an insulating film having a predetermined
thickness, and after this, the conductive caps are separated from
the resin layer for forming an insulating film, whereby the
insulating film is formed on the opening end surface of the each
conductive cap and its vicinity of the end surface by the transfer
method, and after the transfer step, the insulating film is dried.
As a result, the insulating film can be formed on the plurality of
conductive caps efficiently and securely.
[0185] The resin for forming an insulating film preferably has a
viscosity at about 25.+-.5.degree. C. of about 5000 cps to about
20000 cps, such that an insulating film having excellent electrical
insulation properties can be formed securely and easily by
repeating the transfer process at a predetermined number of cycles
until the insulating film has a film thickness so as to secure
sufficient electrical insulation when the insulating film is formed
on the conductive cap by the transfer process.
[0186] According to the method of forming an insulating film of
various preferred embodiments of the present invention, a material
formed in a cap shape is anodization-treated whereby an insulating
film can be formed on the surface of the portions of the cap-shaped
material to be contacted with the terminal electrodes. The
resulting conductive cap alone can be bonded to the substrate by an
adhesive or other suitable joining material or method. Thus, an
electronic component having a greatly reduced height is efficiently
produced.
[0187] It should be understood that the foregoing description is
only illustrative of the present invention. Various alternatives
and modifications can be devised by those skilled in the art
without departing from the invention. Accordingly, the present
invention is intended to embrace all such alternatives,
modifications and variations that fall within the scope of the
appended claims.
* * * * *